The present invention relates to dielectric ceramic compositions for microwave applications and, more particularly, to Bi2O3xe2x80x94ZnOxe2x80x94Ta2O5 dielectric ceramic compositions for microwave devices.
In recent years, communication systems have developed which use microwaves (frequency band ranging from 300 MHz to 300 GHz). These systems include wireless telephones, car phones, cellular phones, satellite broadcasting systems, and the like. As a result, there is an increasing demand for dielectric ceramics with better electrical properties for use components such as resonator devices, band pass filters, and microwave integrated circuits.
Bismuth based pyrochlores have recently become of interest for use as high frequency dielectric materials. One of the bases for this interest is that: they can be fired at low temperatures. In contrast to conventional microwave dielectric materials which require sintering temperatures of more than 1600xc2x0 K, Bismuth pyrochlores can be sintered at less than about 1400xc2x0 K. In addition, their dielectric properties such as a low loss of tan xcex4 of 10xe2x88x924 and a K of up to about 150 make Bismuth pyrochlores promising dielectric material candidates.
For use in microwave communications systems which operate at high frequencies, dielectric materials should have properties such as high dielectric constant (xe2x80x9cKxe2x80x9d); high quality factor (xe2x80x9cQxe2x80x9d); and stable temperature coefficient of capacitance (xe2x80x9cTCCxe2x80x9d). However, it is very difficult to develop dielectric materials which have a stable TCC as well as high K and high Q. A need therefore continues to exist for a dielectric material which has a high K, a high Q value and a stable TCC.